1. Field of the Disclosure
The present disclosure relates to an image forming apparatus, such as a printer, a copier, a multifunction peripheral, and a fax machine, including a dehumidification heater for heating housed sheets, and to a control method therefor.
2. Description of Related Art
Some image forming apparatuses house therein a plurality of sheets. When the sheets absorb moisture, it is sometimes the case that creases or jam (being stuck) is likely to occur at the time of conveyance and fixation. In addition, for example, when moisture (water vapor) enters in between sheets, the sheets may adhere to one another, causing multiple sheet feeding of sheets (conveyance of sheets stacked one on top of another). Accordingly, a dehumidification heater may be provided inside an image forming apparatus in order to remove moisture.
For example, the following sheet feeding apparatus is known. Specifically, the known sheet feeding apparatus includes, inside a main body housing thereof that houses a large number of print sheets: a feeding mechanism for sequentially feeding the print sheets; a dehumidification heater disposed inside the main body housing; internal temperature measuring means for measuring an internal temperature of the main body housing; external temperature measuring means for measuring an external temperature of the main body housing; and dehumidification heater control means for controlling the drive of the dehumidification heater based on the temperatures respectively measured by the external temperature measuring means and the internal temperature measuring means. This configuration is designed to prevent a decrease in life of a photosensitive member due to a significant temperature increase inside the main body housing caused by the dehumidification heater being driven continuously, and an unnecessary increase in power consumption caused by driving the dehumidification heater even in a situation where no dehumidification is required.
First, on the image forming apparatus, a control unit (controller) for controlling the energization of the dehumidification heater in the sheet feeding unit is mounted. For example, the control unit recognizes the humidity based on an output of a humidity sensor. Then, the control unit energizes the dehumidification heater when the humidity is equal to or higher than a certain value, and cuts off the energization of the dehumidification heater when the humidity falls below the certain value, to thereby control drying of the sheets.
On the other hand, in recent years, a power saving mode is provided in image forming apparatuses due to a rise in the awareness of the energy saving. In the power saving mode, power supply to parts constituting the image forming apparatus is stopped, thereby reducing the power consumption in a standby state. Depending on image forming apparatuses, parts whose power supply is stopped in the power saving mode are different. In general, when there are a larger number of parts whose power supply is stopped, a higher power-saving effect is achieved. Accordingly, power supply to the control unit of the image forming apparatus may be stopped.
Thus, with a transition to the power saving mode, power supply to the control unit which controls the operation (energization) of the dehumidification heater may be stopped. In such a case, during the power saving mode, control over the dehumidification heater and checking of the humidity are not carried out. On the other hand, in order to adequately dehumidify the sheets, it is necessary to maintain the energization of the dehumidification heater for a specified period of time. For this reason, during the power saving mode, the dehumidification heater may be maintained in the same state (ON state or OFF state).
However, in the case where the power saving mode continues for a long period of time, when the dehumidification heater is maintained in the ON state, dehumidification is continued even though the sheets have dried, resulting in the continuation of wasteful dehumidification. On the other hand, when the dehumidification heater is maintained in the OFF state for a long period of time, the sheets absorb moisture, which may cause a trouble in sheet feeding or conveyance.
Accordingly, it is conceivable to resume power supply temporarily and regularly to drive the control unit even in the power saving mode in order to switch the ON/OFF of the dehumidification heater in the power saving mode. In this case, start-up of the control unit, checking of the humidity, and switching the ON/OFF of the dehumidification heater are carried out.
However, overly frequent resumption of power supply to the control unit leads to a problem that the power-saving effect obtained from the power saving mode is lost. On one hand, when the cycle of temporary power supply to the control unit is too long, the time during which the dehumidification heater wastefully operates becomes long even though the humidity is sufficiently reduced. On the other hand, conversely, the sheets may absorb a large amount of moisture. Accordingly, there is a problem that temporary power supply to the control unit needs to be performed in an appropriate cycle (timing) so as not to impair the power-saving effect.
In this respect, no considerations for switching the ON/OFF of the dehumidification heater in the power saving mode and temporary power supply to the control unit have conventionally been made, which is also the case of the publicly-known sheet feeding apparatus described above. Therefore, the above-mentioned problems regarding whether or not to operate the main control unit and the like in the power saving mode, or to temporarily operate the main control unit cannot be solved.